The present invention relates to automatic control circuitry for a remotely actuated power distribution switch, and more particularly, the present invention relates to an automatic resetting subcircuit within a remote control circuit for a power distribution switch.
For years, air switches have been provided on power distribution poles as well as in subterranean power distribution vaults to enable the power distribution company to interrupt its circuits for maintenance and to cope with circuit overloads and failures. Typically, the switches have been operated by hand, with switches mounted atop power distribution poles being operated from the ground by manual movement of a handle at the base of a vertical rod linked to the air switches at the top of the pole. In those cases operation of the switches, particularly in emergencies has been delayed by the travel time of a technician to the location of the switch.
More recently, it has been proposed to provide a remotely controlled mechanical operator at the base of the power distribution pole, or in the subterranean distribution vault, for the purpose of opening and closing the switches. Typically, such operators include a housing secured to the power pole enclosing a hydraulic ram movable between two extreme positions. The ram moves the vertical rod operating the air switches through appropriate linkages. A reservoir, four-way valve, and hydraulic pump and motor are provided as well as a pressure accumulator so that in the event of a power failure, pressure from the accumulator may be utilized to drive the hydraulic ram to operate the switch. One such operator is described in U.S. Pat. No. 3,806,679 to Pahl. The Pahl system includes a four-way solenoid valve between the hydraulic ram and the rest of the hydraulic circuit. The four-way valve is provided to reverse the flow of hydraulic fluid in the ram to control its movements from one extreme position to the other, in accordance with the position of the valve. The valve is provided with two solenoid windings to move a valve element in both directions between its two operative positions.
The applicant's prior invention, disclosed in U.S. patent application Ser. No. 584,569, filed on Apr. 8, 1975, now U.S. Pat. No. 4,045,714, for Remote Switch Control and Status Indicator System, described a circuit for actuating one of the solenoids of the four-way hydraulic valve in accordance with a command signal from a centrally located control point removed from the power distribution switch. While the applicant's prior invention inter alia solved a problem with the remote actuation hydraulically driven power distribution switches via voltages received from the telephone line, and has enjoyed considerable commercial success, still some problems have persisted in the cases of power distribution switches exposed to severe weather conditions and climate. For example, in winter ice storms, ice accumulations on the power distribution switch may preclude its movement in response to the hydraulic ram when a remote signal is received, unless the ice is first broken.
The pressure of accumulators of the hydraulic actuator for power distribution switches such as the type shown in the Pahl patent typically have the capacity to enable the hydraulic ram to be actuated several times even when no power is available to operate the hydraulic system pump. One drawback of the applicant's prior control circuit invention, application Ser. No. 584,569, was that once triggered, the circuit would not reset unless the distribution switch actually moved. Thus, one drawback of applicant's prior invention was that in the event of icing or corrosion or some other temporary impediment blocking operations of the switch, once the remote control circuitry operated, there was no way to restore the four-way hydraulic valve to its initial position to enable repeated attempts to overcome the ice, corrosion, etc. and operate the switch.
The applicant has found that if the hydraulic ram of the hydraulic actuator system is operated repetitively, often, ice formation, corrosions or other impediments to movement of the power distribution switches are overcome and the switches may then be actuated in the direction, and to the position, intended. Thus a need has arisen for an automatic reset circuit enabling the four-way hydraulic valve to be returned to its initial position shortly after an attempted operation of the switch in the event that it does not move in response to the force on the vertical rod applied by the hydraulic ram. Thus, the present invention enables the control circuit of the applicant's prior invention to be actuated again, and again, until the ice, corrosion or other impediment gives way and the switch moves.
An object of the present invention is to provide an automatic reset circuit for resetting an electromechanical control element in an automatic actuation machanism for a power distribution switch in the event that the switch is temporarily inhibited from operation.
Another object of the present invention is to provide an automatic reset subcircuit which is compatible with a remote control circuit connected to control the actuation mechanism for a power distribution switch.
A further object of the present invention is to provide an automatic resetting subcircuit for a remote control circuit operating the actuation mechanism for a power distribution switch which is characterized by few electrical components, low cost in manufacturing, and reliability in operation.
Yet another object of the present invention is to provide an automatic resetting subcircuit for a remote control circuit for the actuation mechanism controlling a power distribution switch which is fabricated in a small self-contained plug-in unit which may be readily removed and easily replaced thereby facilitating maintenance of the system.
The automatic resetting subcircuit of the present invention works in conjunction with a remotely actuated power distribution switch control circuit. The control circuit is operatively connected to a two position electromechanical control for the actuation mechanism for operating the switch. The control has two electrical elements, each element for moving the control in an opposite direction between two positions corresponding to the open and closed positions of the distribution switch. A first energy storage capacitor stores energy received from a source remote from the remote control circuit, and a locally signalled control subcircuit applies the energy stored in the first energy storage capacitor to one of the elements of the electromechanical control to cause the switch to be operated in a predetermined direction. The automatic resetting subcircuit includes a second energy storage capacitor for storing energy received from the remote source, the second energy storage capacitor being non-responsive to the operation of the first control subcircuit. A sensor switch responsive to the position of the power distribution switch, is connected to the first and second energy storage capacitors for reversing the connections thereto between the control subcircuit and the automatic resetting subcircuit in accordance with the position of the distribution switch. A time delay circuit provides a predetermined time delay within the automatic resetting subcircuit. A reset circuit closure element is connected to the second energy storage capacitor and the other element of the electromechanical control through the sensor switch. A control element on the reset circuit closure element is connected to the time delay circuit, and to a level sensor connected to the first energy storage capacitor so that the reset subcircuit comes into operation in the event that the switch has not been operated despite the actuation of the control subcircuit. The reset subcircuit then returns the electromechanical control to its initial position after said predetermined time delay.
Other objects, advantages and features of the present invention will become apparent from the following detailed description of a preferred embodiment in conjunction with the accompanying drawings.